weeks] PALEONTOLOGY, PETROLOGY, AND MINERALOGY, 1894. 103 
631a Williams (George Huntington). Piedmontite from a new locality. 
Abstract : Am. Nat., vol. xxviii, pp. 517-518 (f p.). 
Noticed in Bibliography and Index for 1892 and 1893. 
G38 and Clark (W. B.). Outline of the geology and physical 
features of Maryland. 
Johns Hopkins Univ. Press, Baltimore, Md., 1893. 
Abstract: Am. Jour. Sci., 3d ser., vol. xlvii, p. 320 (-£ p.y. 
This is a reprint of chapters relating to physical geography and 
geology from the Avork entitled " Maryland and its Resources, " pre- 
pared by members of the Johns Hopkins University faculty for the 
World's Columbian Exposition. 
G38« McGee (W J), Willis (B.) and Darton (K H.). Geology 
of Washington and vicinity. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 219-251. 
See McGee (W J), Willis (B.), Darton (N.H.), and Williams (G. H.), 
No. 385. 
G39 Williams (Henry Slater). On the age of the manganese beds of 
the Batesville region of Arkansas. 
Am. Jour. Sci., 3d ser., vol. xlviii, pp. 325-331. 
Reviews the discussion as to the origin and age of these beds by 
R. A. F. Penrose, and discusses the paleontologic evidence which 
indicates that the manganese occurs at a distinct horizon between two 
limestones— the lower one containing Ordovician species which have 
been found in rocks called Upper Silurian, and the upper limestone 
carrying an Upper Silurian fauna which has been reported from 
Lower Silurian horizons. 
040 [Correlation of clastic rocks.] 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 170-171. 
Remarks on the importance of considering the relation of organisms 
to conditions of environment. 
641 Dual nomenclature in geological classification. 
Jour, of Geol., vol. ii, pp. 145-160. 
Abstracts: Am. Jour. Sci., 3d ser., vol. xlvii, pp. 143-145; Am. Geol., 
vol. xiii, pp. 139-140. 
Discusses the value of the time scale and formation scale in geologic 
classification. 
641a Willis (Bailey). Relations of synclines of deposition to ancient 
shore lines. 
Abstract: Am. Geol., vol. xiii, pp. 140-141. 
Mlb McGee (W J), Williams (G. H.), and Darton (N". H.). 
Geology of Washington and vicinity. 
Int. Cong. Geol., Compto Rendu, 5th session, pp. 219-251. 
See McGee (W J), Williams (G. H.), Willis (B.) and Uarton (N. II.), 
No. 385. 
042 Williston (S. W.). Kansas pterodactyls. 
Kans. Univ. Quart., vol. 1, pp. 1-13, pi. 1, and vol. ii, pp. 79-80. 
Gives a list of Pteranodon species hitherto named, and describes 
some of their characters and those of Nyctodactylus. 
